US2026988A - Road paving - Google Patents

Description

0R 2,026,9 EX

Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE ROAD PAVING of Delaware No Drawing. Application November 1, 1930, Serial No. 492,875. In Germany November 5, 1929 Claims.

My invention relates to road-pavings. My invention has particular reference to the making of rolled ballast roads.

It is an object of my invention to provide a 6 road which has the tensile strength, hardness and wearing quality of a concrete road combined with the resistance to temperature changes, etc. of an asphalt road.

Many suggestions for making so-called asphalt-concrete roads have already been made but the proposition was always to apply to the road a mixture of asphalt and concrete. Various hydraulic binding matters, such as cement, lime, gypsum and the like, or a mixture of such sub- 1 stances, or a bitumen, in the condition of a powder or an emulsion, were added to the mixture. My invention departs altogether from what has'already been suggested, its object being, as mentioned, to impart to a ballast road the prop- 20 erties of a concrete road and of an asphalt road. To this end, I lay a road-paving including ballast and a pulverulent mixture of a hydraulic binding matter with a bituminous substance filling the interstices between the ballast stones, roll the paving and wet the rolled paving with water,

with or without the addition of means for facilitating penetration and binding.

According to my invention, consequently, I do not lay a mixture of asphalt and concrete, but the 30 ballast. Before the ballast is rolled the pulverulent mixture of a hydraulic binder and bituminous matter is spread on the ballast, or raked, so that it will penetrate into the interstices between the ballast stones, whereupon the pavement is treated further. This is an absolutely novel system of making ballast roads which has never been performed heretofore. The ballast stones in the road are united by a hydraulically set uniformly bituminated mortar which is usually applied in pulverulent form and mixed with water in situ. The mortar advantageously comprises g. n i r ijj n ma eria consis in per CED O W -re substantially of a Bituminous suBst selectedfrom a class cdnsfiting of aspfialt, tar and pitch.

a c ass consisting of gypsum lime with a small amoun not substantially over '7 or of a solution. It may also be added after the hydraulic binder has been rolled into the ballast, by squirting or pouring it on the rolled ballast.

Suitable hydraulic binders are gypsum or a 6 mixture of gypsum with lime or cement.

Heretofore it was impracticable to use gypsum as a binder for roads as its setting, if applied as wet mortar, was too rapid. Ii gypsum were admixed to the ballast in a mixing machine it 10 would become solid before the mortar could be laid on the road.

This invention permits applying gypsum to the road in the simplest manner, and to fill the interstices between the ballast stones, and to connect the stones without the gypsum binding before the ballast is rolled. Gypsum as mortar has the particular advantage that on account of its high porosity it can be impregnated thoroughly at low cost and in various ways. Suitable impregnating agents are mineral salts such as water soluble salts of borates, phosphates, fluor-silicates, alums or chlorides of alkaline earth metals, and watery emulsions of tar or other bituminous matter. It is even possible to effect the impregnation with Trinidad asphalt, hard bitumen known as Mexphalt" or soft bitumen known as Spramex dissolved in chlorinated or other hydrocarbons, or tar. In this manner, a binder is provided as the bearer of asphalt, tar and the like which is able to absorb large quantities of substances which harden the paving and render it weather-proof. The properties of the paving may be varied by suitably selecting the admixtures to the binder.

It has been found that gypsum has the remarkable property of absorbing 10% or more of road tar and still being in pulverulent condition. It

-may even be stirred with water and binds equally well without tar, but the binding is much slower. The mortar thus obtained, after having bound completely, and become dry, is superior to gypsum without tar in that it is water-proof. This opens up to gypsum a new and very large field of application, and a very cheap material for binding the stones or ballast is provided which is also suitable as a coating for treating road surfaces with split, 1. e. very finely disintegrated stone ballast, and the like. It has also been found that gypsum with 5 to '1 bituminou is advantageous and has similar properties. Consequently, this invention provides a new mortar in which two substances of distinct properties, an organic water-repellent substance, viz., tar or other bituminous matter 55 and a water-binding substance, viz., gypsum, hydraulic lime or cement are combined in pulverulent form and in marketable condition which are mixed with water in situ to serve as binding matter for ballast, split and the like. When the hydraulic binder sets there results a monolithic block. This was not practicable and not known heretofore. Such mortar has extraordinary possibilities for the future.

Bitumination of gypsum has been found to be practicable in three ways, as follows:

1. Cold gypsum is impregnated with tar or bitumen dissolved in organic hydrocarbons by treating it in so-called friction mills, such as mixers of the Eirich type, disintegrators, colloid mills, and similar apparatus.

2. It is still better to admix the tar or bitumen to the pulverulent gypsum in the condition in which it is discharged from the gypsum boiler, that is, hot, and to treat the mixture as described under (1).

3. The most economical and simplest method is adding the tar or bitumen directly in the gypsum boiler, the advantage being that boiling, bituminating, and tarring are performed in a single operation, reducing very much the cost of this so-called bituminous gypsum as subsequent treatment is not required. By adding the bitumen during the boiling of the gypsum, the boiling may be regulated which is a particularly desirable factor in the manufacture of gypsum.

It has been found that cement, lime and other hydraulic binders may be added with advantage to the gypsum before the bitumination or tarring and that the mortar is improved by tarring or bituminating a mixture of gypsum with lime or cement.

This novel compound for road-making and for building generally possesses important technical advantages. Bituminated or tarred gypsum, as described above may not only be used as binder or mortar but it may also be added to dry cement and (or) lime as a bitumen-containing filler, at the rate of 10 to 35%. In the latter case it has been found that tar up to the proportion of 25%, calculated on gypsum, may be precipitated on gypsum and that such tarred bituminated gypsum does not exert the detrimental effects on cement and (or) lime as does gypsum, tar or other bituminous matter if added separately; that is, the cement substantially retains its original hydraulic properties and attains its usual tensile strength, hardness and resistance to wear. By adding to cement and (or) lime, gypsum containing tar or other bituminous matter at the rate of only to not only the mortar will bind more rapidly, but its resistance to moisture is also improved. Thus bituminated gypsum is very useful not only as a binder but also as a filler for cement and (or) lime.

In order to improve an old, water-bound ballast road, I proceed as follows: Loose dirt, loam, and the like are removed by squirting the ballast with water. After the road has been cleaned, a uniform layer of coarse ballast, the size of the stones being 3 /8 to 4% in., and pulverulent alabaster or stucco gypsum, better still hydraulic gypsum is applied, all cavities between the stones of the ballast being uniformly filled by raking the gypsum. The gypsum is admixed at the rate of 5 to 25 kgs. per sq. m., in accordance with the density of the traflic on the road. The ballast is now rolled with a street roller weighing 8 to tons until the ballast has set. After the rolling, water is applied to the road in such quantities as to enable the gypsum to combine into gypsum mortar with the water, and to connect the ballast stones. Any suitable means may be used for applying the water, such as sprinkling appa- .ratus, sprinkling cars and the like, for instance, 5

a normal tar sprinkler having a nozzle, or an emulsion sprinkler, also with a nozzle. In order to facilitate the penetration of the water, it may be mixed with a wetting agent, such as alcohol, acetone and similar substances at the rate of 10 1 to 5%. When it is desired that the binding should be less rapid small quantities of glycerin, sulfite liquor and other emulsifying agents are added to the water at the rate of .1 to 1%. A paving thus treated becomes hard within 15 15 minutes, after 30 minutes it is already quite firm and in the warm season it becomes dry to such an extent within 2 to 3 hours that it may be impregnated. However, if possible, the gypsum mortar should be allowed to become thoroughly dry, and a longer period than 2 to 3 hours should elapse before the impregnation. If desired the ballast may be rolled immediately after the water has been applied and before the mortar has finally set.

Suitable impregnating agents for the gypsum are diluted emulsions of bitumen or tar containing under 50% of bitumen, preferably 10 to 20%. Such diluted emulsions penetrate excellently into the porous gypsum mortar, changing it into 8379- sum-bitumen mortar. Such mortar is a first-class paving and is much more solid and strong than the so-called impregnated sand-bitumen ballast because the binding power of the bitumen is added to that of the gypsum mortar.

In cities where the streets were hitherto paved with compressed asphalt, this invention is particularly useful in providing a substitute for compressed asphalt. A layer of gypsum mortar is impregnated with asphalt dissolved in chlorinated hydrocarbons or other hydrocarbons or artificial hard bitumen dissolved in a corresponding liquid. With solutions of this kind which are sufficiently diluted, viz., at the rate of 5 to 50%, according to the more or less good condition of the gypsum mortar, a rapidly binding paving is obtained which is equal to a paving of compressed asphalt. Instead of asphalt or artificial hard bitumen, the solution may also contain viscous binding agents for hard-macadam asphalt. As a rule, it is not necessary to subsequently coat the pavement with a layer of bituminous matter except if, in order to obtain a rough surface, an emulsion of bitumen or tar is applied, and split is spread on the emulsion, and 65 rolled. The split sticks well to the impregnated gypsum mortar, and in this manner, as desired,

a hard, smooth and strong, or a rough surface is obtained which cannot be obtained with other means.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

The percentage of bituminous material called for in the claims is based on the weight of the hydraulic binder, which, of course, is mixed with the usual amounts of sand, etc. for preparation of the mortar.

I claim:

1. A rolled ballast road comprising ballast stones, which are united by a hydraulically set uniformly bituminated mortar filling the interstices between the stones, the said mortar being prepared from an initially pulverulent intimate mixture of a hydraulic binder and not more than seven per cent, calculated on the weight of the binder, of a bituminous substance, so as to form a monolithic block.

2. A rolled ballast road comprising ballast stones, which are united by a hydraulically set uniformly bituminated mortar filling the interstices between the stones, the said mortar being prepared from an initially pulverolent intimate mixture of cement, another hydraulic binder selected from a class consisting of lime and gypsum and not more than seven per cent calculated on the weight of hydraulic binders present, of a bituminous substance, so as to form a monolithic block.

3. A rolled ballast road forming a monolithic block comprising ballast stones united by a hydraulically set uniformly bituminated mortar filling the interstices between the stones, the said mortar being prepared from an M- ulent intimate mixture of a der, selec e mm a c cons sting of an Cme!1,w :m'nl: tially over 7 per cent of organic water-repellent material, consisting substan nous sus ance, ca c a e on the weight of said bin l. I rolled ballast road forming a monolithic block comprising ballast stones united by a hydraulically set uniformly bituminated mortar filling the interstices between the stones, the said mortar being prepared from an initially pulverulent intimate mixture of a hydraulic binder, selected from a class consisting of gypsum, lime and cement, with a small amount not substantially over '7 per cent of organic water-repellent material, consisting substantially of a bituminous substance, calculated on the weight of said binder; the said pulverulent mixture of binder and bituminous substance being mixed with water 15 and hydraulically set in situ.

5. The rolled ballast road of claim 1 wherein the hydraulic binder is selected from a class consisting of gypsum, lime and cement, and wherein the said bituminous substance is selected from a 20 class consisting of aphalt, tar and pitch.

HERMANN PLAUSON.